1. Field of the Disclosure
The present subject matter relates to the assembly of components for making radio frequency identification (“RFID”) devices, more particularly using RFID chips themselves to facilitate assembly of RFID devices and the devices thus assembled.
2. Description of Related Art
RFID tags and labels (collectively referred to herein as “devices”) are widely used to associate an object with an identification code. RFID devices generally have a combination of antennas and analog and/or digital electronics, which may include, for example, communications electronics, data memory, and control logic. RFID devices typically are used in conjunction with retail security systems, security locks and ignitions in vehicles, for access control to buildings, and for tracking inventory and parcels. Some examples of RFID tags and labels appear in U.S. Pat. No. 6,107,920; U.S. Pat. No. 6,206,292; and U.S. Pat. No. 6,262,692, all of which are hereby incorporated herein by reference in their entireties.
Automatic identification of products using RFID technology has become ubiquitous. RFID technology devices include electronic components that respond to radio frequency (“RC”) commands and signals to provide identification of each device wirelessly. Generally, RFID tags and labels comprise an integrated circuit (“IC”, or chip) attached to an antenna that responds to a reader using radio waves to store and access the information in the chip. Specifically, RFID tags and labels have a combination of antennas and analog and/or digital electronics, which often includes communications electronics, data memory, and control logic.
One of the obstacles to more widespread adoption of RFID technology is that the cost of RFID devices, particularly tags, and difficulties for optimization of economical manufacturing of RFID tags. Increased demand for RFID tags has manufacturers seeking cost reduction and manufacturing simplification. Assembly difficulties tend to increase as RFID chips and their components become smaller. For example, to interconnect the relatively small contact pads on the chips with the antennas, intermediate structures variously referred to as “straps,” “interposers,” and “carriers” are sometimes used to facilitate inlay manufacture. Interposers include conductive leads or pads that are electrically coupled to the contact pads of the chips for coupling to the antennas. Small RFID components need to be assembled, at times through the use of adhesives. Often those adhesives require the application of energy in order to transform them from their uncured state to a cured state at which they hold two or more components together in the course of making, storing, transporting and using the finished RFID device. Usually, this assembly procedure must meet a requirement of providing effective electrical connection between the chip and the antenna.
Typically the various elements that are assembled to form a complete RFID device are provided arranged on linear arrays such as on a substrate, tape or web. The respective webs are directed to a joining location and then are assembled together by application of heat (or other energy sources) and pressure to uncured adhesives, which energy and compression are maintained for a length of time during the assembly process until the adhesive is sufficiently cured and the components securely held together by a cured adhesive joint. This requires a separate curing and compression action during the course of the assembly operation, which can be especially problematic and capital intensive to implement measures and provide equipment that accommodate moving webs and other production details preferred for high-speed assembly manufacturing of very small components into small RFID devices which must be achieved without significant reduction in RFID operation and effectiveness.
For example, a typical method of attaching RFID chips to straps or antennas (or other components) involves multiple steps including: (a) picking the chip off the wafer, (b) flipping the chip so it is held by its back surface, (c) placing the chip onto the strap or antenna with its connections oriented over bond pads, (d) placing onto an adhesive, which can be a non-conducting or an anisotropic material, and (e) curing the adhesive by placing a metal block, referred to as a “thermode”, on top, which applied heat and pressure typically is in conjunction with a heater below the web. Transferring heat via conduction through the silicon and/or the plastic substrate is relatively slow, and curing time can be a significant factor in the throughput in units per time period of production during the manufacturing process.